Dynamic phytoplankton iron physiology and its impacts on global ecosystem function

Dr Tom Bibby, Prof Christopher Moore, Dr Maeve Lohan

Primary production couples solar energy arriving at the Earth’s surface to global biogeochemistry, linking elemental cycles together through the synthesis of organic molecules. In particular, the proportion of carbon to dissolved iron in biological production is a key factor that determines how much carbon can be sequestered across vast regions of the open ocean. If the elemental composition of plankton biomass was fixed, oceanic production in iron-limited regions would be set primarily by the supply of dissolved iron. Indeed, many global ocean biogeochemical models rely on this assumption (1). However, both laboratory experiments (phytoplankton cultures) and oceanic observations indicate marked variability in the iron content of marine phytoplankton and associated particulate organic matter. Despite its importance, phytoplankton iron physiology is currently poorly constrained, especially under dynamic conditions (2). This project aims to address this issue, using experimental cultures of diatom species to better constrain the iron physiology of phytoplankton in a highly dynamic ocean. These experiments will then be used to develop numerical models linking sub-cellular phytoplankton physiology to global biogeochemical cycles (3).


The project will include both laboratory experiments and the development of numerical models. The student will establish cultures of representative diatom species, exposing them to high and low availability of iron and light. The objective will be to measure both the steady state and transient response to different iron and light conditions in terms of cell abundances, physiological indicators (e.g. photophysiology), elemental composition and resource uptake fluxes. These measurements will subsequently be used to test (and improve) current physiological models of phytoplankton growth and elemental composition. It is expected that model development and testing will begin in the relatively simple and highly idealised context of monospecific cultures. After this initial 'reality check', it is expected that more realistic models will be developed to include a more complex representation of the global plankton food-web.


University of Southampton

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted in the School of Ocean and Earth Science. Specific training will include relevant aspects of plankton physiology (cell cultures, radio-isotopes), biogeochemistry (global biogeochemical cycles and stoichiometry), and numerical modelling (phytoplankton physiology and ocean ecosystems). The project will require interaction with a wide range of world-class researchers in ocean biogeochemistry and ecology in Southampton, and we expect the student will have the opportunity to participate in at least one ocean-going research expedition.


Eligibility & Funding Details: 

Please see https://inspire-dtp.ac.uk/how-apply for details.

Background Reading: 
  1. A. Tagliabue, et al., How well do global ocean biogeochemistry models simulate dissolved iron distributions? Global Biogeochemical Cycles 30, 149–174 (2016).
  2. Polyviou, D., Baylay, A. J., Hitchcock, A., Robidart, J., Moore, C. M., & Bibby, T. (2018). Desert dust as a source of iron to the globally important diazotroph Trichodesmium. Frontiers in Microbiology, 8, [2683].3. B. A. Ward, et al., EcoGEnIE 1.0: Plankton Ecology in the cGEnIE Earth system model. Geoscientific Model Development doi.org/10.5194/gmd-2017-258, 4241–4267 (2018).